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' G. lVI. DAVIS 8v A. BEMENT.

BACK PRESSURE VALVE.

No. 410,538. Patented Sept. 3, 1889.

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UNITED STATES PATENT OEEICE.

GEORGE M. DAVIS AND ALBURTO BEMENT, OF CIIICAGO, ILLINOIS; SAID BEMENT ASSIGNOR TO SAID DAVIS.

BACK-PRESSURE VALVE.

SPECIFICATION forming part of Letters Patent No. 410,538, dated September 3, 1889. .Application tied April 2, 1889. seminasoa'ls. (Nomodel.)

- To @ZZ whom t may concern.-

Be it known that we, GEORGE M. DAVIS and ALBURTo BEMENT, citizens of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented cert-ain new and useful Improvements in Back- Pressure Valves, of which the following is a full, clear, and exact description, that will.

enable others to make and use the same, reference being had to the accompanying' drawings, forming a part of this speciiication.

The object of this invention is to provide an improved valve to be located in the exhaust pipe or passage leading from. the cylinder of a steam-engine, for the purpose of regulating and preventing anyback-pressure from affecting the free working of the engine when the exhaust-steam is sought to be utilized for heating or other purposes, as will be hereinafter set forth. The construction of the valve proper is on the differential system, two valves of different diameters being used in the exhaust-passage, and having an intermittent action in accordance with the difference of pressure.

Figure l is a side elevation showing the exterior arrangement; Fig. 2, a transverse section of the same; Fig. 3, a vertical section in plane 3, Fig. 2; Fig'. at, a sectional detail of the larger valve, and Fig. 5 a plan of a springplate used on the larger valve.

Referring to the drawings, A represents `the body or casing inclosing the valve-chamber A and valve parts; A2, the inlet and A3 the exit passage. The valve-chamberis provided with the two exit-openings a a', differing in area. The larger valve B is located in the opening' d in the valve-chamber and the lesser valve C in the opening a', the two valves being rigidly connected by the stem a2.

The stud d3 has a threaded engagement (see Fig. 4) in the outer side of the valve B. To the projecting end of this stud is pivoted one end of the link a", connecting with the crank-arm a5, mounted on the rock-shaft D. The inside end of this shaft is provided with a journal-bearing in the inner side of the chambered cap or chest E, bolted to the valve-casing and extends through the eX- terior bearingsleeve F to the outside, as

shown in Fig. 3. One end of the sleeve F is inserted in the chambered cap F.. The opposite end, being threaded and in connection with the gland or packing-nut b, forms the stuffing-box b.

The notched weightflever G is mounted 011 the outer projecting end of the shaft D, and has the reg'ulating-weight d hung thereon. This lever G is secured to the shaft D by the set-screw d.

The valves B and C are provided with guidelugs g g', which retain the same in their proper position. The spring-plate I-I, secured on top of the larger valve B, prevents the valves from seating with a jar and imparts a comparatively noiseless action, as the curved ends h of the spring will first have contact and cushioning with the surface on each side of the valve-seat and ease the seating of the valves, thus remedying one of the objectionable features incident to devices of this characier.

Another important feature of this device is, that a much smaller weight can be used, as only the difference in area of the two valves must be weighted against. Under the ordinary arrangement the full area of the eXhaustpassage had to be weighted back, requiring a l weight in the proportion of about twelve to one.

The chamber-cap bolted to one side of the valve-chamber provides for convenient access to the interior parts.

Having thus described our invention, what we claim as new, and desire to secure by Letters Patent, is

1. In a back-pressure valve, the combination, with a valve-chalnber having' two exhaust-openings of different areas, of the differential valves located in said openings and connected by a stem common to both, the spring-plate secured to the larger of said valves and cushioning' the action of the same,

-the stud a3, the link d'1, the crank-arm, the

shaft on which said crank is mounted inside of the valve-casing, and the weighted lever mounted 011 the outer projecting end of said shaft, substantially as and for the purpose set forth.

2. In a back-pressure valve, the combina- IOO JLion of the valve-casing, the differential of said shaft, substantially as and for the Valves ehambered therein, the spring-plate purpose set forth. cushioning the action of said valves, the

chamber-ed oep bolted to one side of said eas- 5 ing, the connecting-link and crank,the rockshaft located inside of said cap, the bearingy Witnesses:

sleeve through which said shaft passes, and L. M; FREEMAN,

the Weightedlever mounted on the outer end'. f.' J. B; DONALDSON. 

